Downward access spline for demountable suspended ceiling system

ABSTRACT

A device for installing a demountable suspended tiled ceiling system constructed of parallel primary support members fixedly suspended from the upper part of a building space and spaced from each other, and T-type intermediate support members extending between, and resting upon the shoulders of adjacent primary support members. In this system, at least one of said intermediate support members is constructed of two disengageable L-shaped halves adapted to be joined back-to-back and latched together to form a T-spline. One of said halves is shorter than the distance between adjacent primary support members. The tiles are of such total length that when rabbetted at their upper edges of each end, they fit against the sides of the primary support members and overlap one half of the width of the bottoms of said primary support members. Thereby the tiles may be mounted flushly in end-to-end abutment. The tiles are slotted laterally to receive the flanges of the T-type intermediate support members. When it is desired to remove the tiles, a protruding wire tab from the disengageable intermediate support member may be pushed upwardly to lift the latter and shift it relative to the longer half to disengage it therefrom so that the shorter half may be pulled down with the tile which it supports. Whereupon the other longer half may be removed from the adjacent tile by sliding it laterally and that tile also pulled downwardly for removal.

United States Patent 1 Stanley A 51 Feb. 20, 1973 [54] DOWNWARD ACCESS SPLINE FOR DEMOUNTABLE SUSPENDED CEILING SYSTEM [75] Inventor: John E. Stanley, La Canada, Calif.

[73] Assignee: Duo-Flex Corporation, Glendale,

Calif.

[22] Filed: June 7, 1971 [2]] App]. No.: 150,549

[52] US. Cl. ..52/484, 52/488, 52/489 [51] Int. Cl. ..E04b 5/52 [58] Field of Search ....52/488, 484, 483, 478, 489,

Primary ExaminerPrice C. Faw, Jr. Attorney-Smyth, Roston & Pavitt [57] ABSTRACT A device for installing a demountable suspended tiled ceiling system constructed of parallel primary support members fixedly suspended from the upper part of a building space and spaced from each other, and T- type intermediate support members extending between, and resting upon the shoulders of adjacent primary support members. In this system, at least one of said intermediate support members is constructed of two disengageable L-shaped halves adapted to be joined back-to-back and latched together to form a T- spline. One of said halves is shorter than the distance between adjacent primary support members. The tiles are of such total length that when rabbetted at their upper edges of each end, they fit against the sides of the primary support members and overlap one half of the width of the bottoms of said primary support members. Thereby the tiles may be mounted flushly in end-to-end abutment. The tiles are slotted laterally to receive theflanges of the T-type intermediate support members. When it is desired to remove the tiles, a protruding wire tab from the disengageable intermediate support member may be pushed upwardly to lift the latter and shift it relative to thelonger half to disengage it therefrom so that the shorter half may be pulled down with the tile which it supports. whereupon the other longer half may be removed from the -adjacent tile by sliding it laterally and that tile also pulled downwardly for removal.

4 Claims, 10 Drawing Figures PATENTEUFEBZOIQTS sum 1 OF 3 Ava/vi);

PATENTED FEB20I975 sum 2 or 3 QM .36 QQQR arramvsr/ PATENTED FEBZOIHYS 7 1 6,956

SHEET 30F 3 DOWNWARD ACCESS SPLINE FOR DEMOUNTABLE SUSPENDED CEILING SYSTEM BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to dismountable suspended ceiling systems and to devices for use in assembling and installing the same.

2. Description of the Prior Art Ceilings suspended below the ceiling which comprises the underside of the flooring for the next floor above or the building roof, have been in use for many decades. With the advent of air conditioning and the need for a plenum into which to draw air from, or from which to dispense it into inhabited room spaces, great impetus was given to the development of many different systems for providing suspended ceilings. Certain of these developments particularly addressed themselves to providing ready demountability as well as to aesthetic appearances, in order that air conditioning and electrical conduits and equipment could be readily serviced without the necessity of destroying any part of the ceiling to obtain access to such equipment.

Almost all suspended ceiling systems in use today involve the use of acoustical tiles of 2 to 4 feet in length and a foot in width. These tiles are ordinarily grooved or rabbetted along certain of their edges to receive, or to rest upon and be supported by flanges of secondary support members, such as T-splines and/or H-members. The T-splines or H-members are ordinarily supported by some type of primary support member, of a T, H or Z variety, which primary support member is hung directly or indirectly by wires or other vertical supporting elements extending down from the transverse wall above which constitutes the next floor in the building. Examples of these various prior art systems may be seen in the following U.S. Pat. Nos.:

Name Number Date W. F. LaMorte 1,218,283 1917 C. F. Davis 1,867,615 1932 W. H. Venzie 1,897,776 1933 C. O. Walper 1,931,713 1933 K. MacLeod 1,984,028 1934 H. W. Brown et al. 1,992,054 1935 A. C. Olsen 2,013,762 1935 F. A. Manske et al. 2,017,911 1935 C. F. Burgess 2,028,272 1936 A. C. Olsen 2,101,952 1937 C. L. Neumeister 2,139,641 1938 A. C. Olsen 2,152,418 1939 W. H. Venzie 2,242,558 1941 .l. A. Chambers 2,270,268 1942 W. Haertel 2,303,271 1942 G. C. Wright 2,307,653 1943 C. C. Droeger 2,309,695 1943 A. C. Olsen 2,318,092 1943 L. F. Urbain 2,340,911 1944 S. R. Naysmith 2,376,715 1945 H. N. Cartwright 2,403,580 1946 R. H. Stitt 2,481,794 1949 H. L. Finch 2,485,090 1949 A. C. Olsen 2,499,278 1950 V. Jacobson 2,648,102 1953 V. Jacobson 2,667,667 1954 Among the more easily assembled and demountable types of suspended ceilings are those disclosed in my own prior U.S. Pat. Nos. 2,742,122; 3,032,833; 3,053,359; and 3,301,165. In each of these patented systems the tiles are supported on their ends by shoulders of the primary support members and/or by T- splines resting on such shoulders. Demountability is accomplished by simply pushing upwardly between any pair of tiles, removing the T-spline which supports the tiles and then removing one or both tiles. The tiles may be replaced by reversing these steps. In U.S. Pat. Nos. 2,742,122 and 3,301,165, the bottom faces of the primary support members are exposed to view. While suspended ceilings installed according to the systems disclosed and claimed in my last two mentioned prior patents offer many other advantages, including an aesthetic appearance and the availability of the primary support members to serve as air conduits and distribution members, or even lighting fixtures, sometimes architects desire that the visible ceiling surface be solely comprised of acoustical tiles which abut in edge-toedge fashion. Such abutment prevents demounting the tiles by simply pushing upwardly since at least one pair of opposite edges of the tiles must overlap a fixed support member. Consequently, in order to provide demountability of the tiles, which abut end to end, some arrangement is required whereby the tiles may be lowered instead of pushed upwardly. Any such arrangement should be simple, easy to install and inexpensive.

There has recently been offered to the ceiling construction industry an arrangement whereby desired downward demountability of tiles in a suspended ceiling is made possible by providing what amounts to a T- spline which is split vertically into two L-shaped halves, each including a vertical web and one of two laterally projecting flanges which together form the transverse base of the T when inverted. These two L-shaped halves may be secured together with their webs backtoback by a pivotable hook-like element, the foot of which extends below the transverse base of the inverted T so formed by the two oppositely extending flanges when the L-shaped halves are so brought together. The hook-like element is pivotally mounted on the web of one of the two halves of the T-spline and latches into a slot in a transverse wall provided to extend from the top of the vertical web of the other of the two halves in a direction opposite to that of the flange of said half, thereby giving said half a Z appearance in cross-section; and said transverse wall is further slotted to pass through it the upper hook-like portion of the pivotable element before it is pivoted into locked position. The first half of the spline is made sufficiently shorter than the Z-half that its ends do not extend to the shoulders or flanges of the primary support members upon which the ends of the tiles and/0r the Z-half of the split T- spline are intended to be supported. Stop means are provided on the Z-half near its extremities in order properly to locate and hold the shorter half against sliding movement relative to the Z-half. Apparently unless such movement is prevented, it might inadvertently disengage the pivotable hook from its receiving slotting.

Such split T-spline has presented certain problems in use which appear to have caused the construction industry not to have widely adopted it as an intermediate support member and this in turn has discouraged use of downwardly dismantable ceiling systems. Among these problems have been the following:

1. It has proved to be somewhat costly to fabricate split T-spline and particularly the shorter half with the pivotable elements. The latter are made separately from the half-T itself and then must be hand-attached to the web of the L-shaped shorter half.

2. If the pivotable elements are too-loosely attached to the web, they can very easily be jarred loose from the slotting in the other half of the split Tspline, whereupon the edge of the tile which they support may drop down slightly or the whole tile may even fall.

3. If the pivotable elements are too-tightly attached to the web, they may be difficult to turn into hooking position.

4. Their protruding tabs are considered to be unsightly by many architects and others. Particularly where efforts have been made to use them to support four foot tiles, at least two tabs must show for each split spline and these are considered quite objectionable.

In view of these problems with the heretofore existing split T-splines, downwardly demountable ceiling systems in which only the tiles are exposed, have not been installed in many new commercial structures. However, there is widespread demand among architects for such ceiling systems. What has been needed is a more effective and practical intermediate split T-spline member than has heretofore been available.

SUMMARY OF THE INVENTION The present invention comprises an improved downward access split T-spline which obviates the problems inherent in the prior art split T-spline j hereinabove described. While the prior arts larger Z- the slits, enables one to lift the L-shaped member and slide it relative to the slotted Z-shaped member.

' Installation of the downwardly demountable ceiling is accomplished in a manner quite similar to that when l the prior art split T-spline is employed up to. the point where the L-spline half is moved into web-to-web abutment with the Z-spline half. However, instead of attempting to hook the individual pivotally elements in the locking slots, the L-shaped half is pushed upwardly to pass the two fixed stampedout hooks through the larger slots and the entire L-shaped member is than shifted, by means of the U-shaped spring-like member, relative to the Z-shaped member to bring its hook tips over the smaller locking slots whereupon the L-shaped half is dropped down so that the hooks are received'in the latter slots.

If desired, the spring-like members may be pinched and removed from the slits so that nothing shows in the ceiling. If properly marked, the clips may be re-inserted in the slits when removal of the tiles is to be accomplished.

BRIEF DESCRIPTION OF THE DRAWINGS where one set of their ends is supported by a primary support member.

FIG. 3 is a side elevation partly in section showing A the split-T device of the prior art in locked position.

FIG. 4 is a side elevation similar to FIG. 3 but showing the removal of a tile and one half of the split-T device of the prior art.

FIG. 5 is a view similar to FIG. 3 but showing use of the improved device of the present invention.

FIG. 6 is a view similar to FIG. 4 but showing use of the device of the present invention.

FIG. 7 is a plan view taken in the direction of the arrows 7 7 in FIG. 5.

FIG. 8 is an enlarged detail of the split-T device of the present invention.

FIG. 9 is a section taken on the line 9 9 of FIG. 5.

FIG. 10 is a perspective view of a modified device.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1 of the drawings, in the downwardly demountable ceiling system in which the device of the present invention is particularly utilizable, ceiling tiles 10 are supported in end-to-end and edgeto-edge abutment in a suspension system which includes a plurality of primary support members 12 held by wires or rigid elements 14 extending down from the building ceiling formed by the next floor or roof (not shown) in a spaced parallel relationship in a manner well known in the art. Each of the primary support members 12, as best seen in FIGS. 3 6, may comprise a web 16, orificed to receive a hook 18 at the lower end, of the element 14, and a pair of oppositely extending flanges 20, 22. The tiles 10, which are rabbetted at 10a to receive a flange 20 or 22, thereby covering the bottom of the primary support members by end-to-end abutment with another tile, are supported on the shoulders 20a, 22a presented by the flanges 20, 22, respectively, of the primary support members 12 by means of a plurality of intermediate T-type support members24, 24a. The members 24a may be ordinary T-splines.

However, the member or members 24 comprise special dismantable devices, such as the prior art device 24, or the device 24 of the present invention.

As shown in FIGS. 3 and 4, each member 24 is made up of a first half 26 which may be a simple L-spline comprised of a web 26a and a flange 26b. However, the web 260 is provided with at least one and preferably two elements 28 each pivotally secured by a rivet 30 to the web 26a to be rotatable about the rivet 30 for an angle of 15 to 25 from the vertical. Element 28 includes a tab 28a which projects below flange 26b and a hook 28b which extends arcuately above the upper edge of the web 26a. The first half 26 is of a length closely approaching, but not greater than, the distance Member 24 also is comprised of a second half 32 I which is of a length equal to the distance between the webs 16 of such adjacently disposed primary support members 12, and includes a web 34 and an oppositely directed flange 36 extending from the lower edge of the web 34. Small raised projections 38 are provided near the ends of the web 34, such projections being separated from each other by a distance equal to the length of the first half 26 of the member 24. Additionally, there may be provided to extend from the upper edge of the web 34 a second flange 40 oppositely directed from the flange 36. The flange 40 is slotted at 42 to permit the hook 28b on the web 26a to pass therethrough and further slotted at 44 to receive the hook 28b when the element 28 is pivoted to move the hook to the left as best seen in the locked position of FIG. 3.

The prior art ceiling is assembled by placing T- splines 24a to rest on opposing shoulders 20a, 22a of adjacent primary support members 12 and inserting the T-spline flanges 24a in the side kerfs b of the tiles 10. However, wherever it is desired to have a tile 10 immediately demountable to provide access to the ceiling plenum 46 immediately above the suspended tiles, a member 24 is utilized in lieu of the ordinary T-spline 24a. The flange 36 of the Z-shaped half 32 is first inserted in the kerf 10b of a tile, the other side of which has already been mounted by a T-spline 24a and the tile 10 thereby supported on the primary support member 12 as is the right hand complete tile 10' in FIG. 2. The flange 26b of the other half 26 of the member 24 is then inserted in the kerf 10b of a tile 10". With the elements 28 moved angularly as shown in FIG. 4, the side of the tile 10" with the half 26 of the member 24 in the kerf 10b may now be moved upwardly to place the web 26a in back-to-back abutment with the web 34 of the other half 32 of the member 24, locating the web 26a properly between the projections 38 and passing the hooks'28b through the slots 42. At this juncture the tabs 28a are shifted to the right so that the hooks 28b are arcuately moved into the slots 44 to locked position as shown in FIG. 4. The kerf 10b in the other side of the tile 10" may then receive a T-spline 24a for mounting in the conventional manner. The result of this procedure will be a ceiling as shown in FIG. 2.

When it is desired to demount tiles 10' and 10" to obtain access to the plenum 46, one pushes the tabs 28a to the unlocked position, as shown in FIG. 4, and pulls the tabs down. When the hooks 28b do not engage the slots 44, the half 26 of the member 24 is unsup ported so that it and the side of the tile 10" into the kerf 10b of which its flange 26a is inserted, will easily drop down for removal. It is then a simple matter to remove the half 32 of the member from the kerf 10b of the tile 10 and to drop down the latter tile as well. Access to the plenum 46 is thus obtained and the tiles 10' and 10" are replaced by the process first above described.

The improved downward access spline of the present invention eliminates the pivotable elements 28 and the necessity for mounting them properly by means of the rivets 30 onto the web 26a of the L-spline 26. Instead, as shown in FIG. 8, L-spline member 26' has stamped out from its web 26a two hook-like elements 28b each of which is bent back upwardly upon the web 260 to project slightly thereabove. The elements 28b are thus fixed with respect to the webs 26a from which they are punched out. In addition, there is further punched in the web 26a a pair of curved slits 27a and 27b. These slits serve to receive the bent ends 29a, 29b of the U- shaped spring clip 29.

The Z-shaped element 32 may be almost identical to the prior art counterpart 32 shown in FIGS. 3 and 4 with the exception being the distance that the slottings 42 and 44' are spaced from the plane of the nearest side of the web 34'. In the prior art devices of FIGS. 3

and 4, since the element 28 must be mounted to pivot on the unflanged side of the web 26a, the slotting 42, 44 should be located as close to the plane of the unflanged side of the web 34 as possible. Even then, the unflanged sides of the webs 36a and 34 can never be brought together more closely than the thickness of the elements 28. By contrast, the hook-like elements 28b of the present device are punched through to the flanged side of the web 26a'.The unflanged sides of the webs 34 and 26a may thus be brought into abutment, except where a slight separation is required in order to accommodate the ends of the U-shaped clip 29. Because of such disposition of the hook-like elements 28b in the present device, the slotting 42' and 44 should be offset more from the plane of the unflanged side of the web 34'.

FIG. 10 illustrates a modification of the spline member 32' in which the upper flange 40 is eliminated in favor of short horizontal projections 40' over which hooks 28a may be dropped, and the ends 32a are formed as T-spline segments spaced from each other by a distance just slightly greater than the length of the L- spline member 26', thereby to provide more stability in the mounting of the member 32 and the tile into the kerf of which its flange 36' is inserted. When the L- spline member 26' is properly hooked into the slots 44, its ends will abut the inner edges of the T-spline segmented ends 32a.

It will be readily appreciated that the L-spline members 26' may be fabricated much more cheaply than the prior art members 26 with their riveted elements 28. Moreover, there is no problem with the members 26' of having to secure proper rotational friction of the elements 28'against the web 26a. The punched out hook-like elements 28b are fixed with respect to the web 26a. Instead of having to manipulate the elements 28 to hook them into the slots 44, it is only necessary with the device of the present invention to push upwardly upon the L-spline 26' by means of the clip 29 and slide the entire L-spline slightly toward the slottings 44 to drop the hook 28a into such slottings, thereby effectively locking the L-spline half 26' in webto-web abutment with the Z-spline half 32'. If desired, the clip 29 may be pinched to remove it from the curved slits 27a, 27b. Demounting of the tiles, is accomplished by simply pushing upwardly on the clip 29 and shifting the L-spline 26 in a direction from slottings 44 toward slotting 42.

The present invention promises to make downwardly demountable ceilings of the prior art typemore easily installable, less costly and more acceptable aesthetically to architects, building owners and their tenants.

I claim:

'1. A downward access disengageable T-spline device for use in demountable supporting at least two tiles of a suspended ceiling system on the opposing shoulders of a pair of parallel primary support members spaced from each other by a predetermined distance, said device comprising:

A. A first half, said first half i. being of a length not greater than said predetermined distance;

ii. having a vertical web and a transverse flange extending laterally from said web;

iii. including at least one hook-like element having hook means, said element being partially punched out of said vertical web and bent back upwardly upon the web to extend its hook means above said web with its hook facing downwardly, and

iv. clip means attachable to said web and extendable below said transverse flange; and

B. a second half, said second half i. being of a length in excess of said predetermined distance such that it may rest on, and be supported by, opposing shoulders of adjacent primary support members;

. including a vertical web; a first transverse flange extending laterally from the lower edge of latter web in a direction opposite to that of the flange of the first half, whereby the two halves may be brought together and secured by placing their webs in abutment to form a T-member; and a second flange extending from the upper edge of said web of the second half in a direction opposite the direction of the first transverse flange, thereby to constitute a member having a Z-type cross section; and

iii. including first slotting in the said second flange to permit said extending hook means to pass upwardly through said second flange, and second slotting to receive said hook means of said hooklike element on the first half when the latter is lifted and shifted relative to the second half, thereby to insert said hook means into the said second slotting and to lock the two halves together in web-toweb abutment with their flanges oppositely directed to constitute an effective T-spline, whereby the ceiling tiles may be demounted by pushing said first half upwardly by means of said clip means and shifting said first half relative to the second half to remove the hook means from the second slitting and to enable it to be drawn downwardly through the first slotting, whereupon, said first'half may be pulled down from its engagement with the second half and the edge of the tile supported by said first half of the device may be lowered and removed from the ceiling.

2. A downward access disengageable T-spline device for use in demountably supporting at least two tiles of a suspended ceiling system on the opposing shoulders of a' pair of parallel primary support members spaced from each a other by a predetermined distance, said device comprising:

A. a first half, said first half i. being of a length not greater than said predetermined distance;

ii. having a vertical web and a transverse flange extending laterally from the bottom edge of said web to constitute an L-shaped member in cross section, and said web being slit to receive a pair of oppositely extending horizontal pins; and

iii. including a pair of hook-like elements each having hook means, said elements being partially punched out of said vertical web and bent back upwardly upon the web to extend their hook means above the web with their hooks facing downwardly; and

iv. clip means, said clip means including a pair of horizontally extending pin-like ends insertable in said slits in the web and being disposed to protrude below said transverse flange; and

B. a second half, said second half i. being of a length in excess of said predetermined distance such that it may rest on, and be supported by, opposing shoulders of adjacent primary support members;

ii. including a vertical web and a transverse flange extending from the bottom edge of the latter web in a direction opposite to that of the flange of the first half, whereby the two halves may be brought together and secured by placing their webs in abutment to form a T-member; and

iii. permitting the hook means of said hook-like elements to be disposed above its vertical web when the first half is placed in web-to-web abutment with the second half and including means to anchor said hook means when the said first half is raised and shifted in a first direction parallel to the second half and then lowered into web-to-web abutment with the second half, thereby to lock the two halves together with their flanges oppositely directed to constitute an effective T-spline; whereby the ceiling tiles may be demounted by raising the first half by the clip means and shifting it in a second direction opposite the first direction, thereby unhooking the hooks of the said hook-like elements from the anchoring means in the said second half, andslidably separating the two halves of said device by pulling downwardly on the clip means, thereby enabling the edge of the tile supported by each said first half of the device also to be lowered and removed from the ceiling.

3. The device as described in claim 2, wherein the means in said second half of said device to anchor the hooks of the hook-like elements of the first half of said device, comprises a further flange extending from the upper edge of the web parallel to, but oppositely from the other flange on said web, and said further flange having first slotting to permit the upper parts of said hook-like elements to be passed therethrough, and second slotting adjacent the first slotting to receive said hooks.

4. A downward access disengageable T-spline device for use in demountably supporting at least two tiles of a suspended ceiling system on the opposing shoulders of a pair of parallel primary support members spaced from each other by a predetermined distance, said device comprising:

A. a first half, said first half i. being of a length not greater than said predetermined distance;

ii. having a vertical web and a transverse flange extending laterally from said web; and

iii. including at least one hook-like element having hook means, said element being fixedly attached to the web of said first half, to extend said hook means above said web with the hook facing downwardly, and iv. wire clip means attachable to said web and extending below said transverse flange; and B. a second half, said second half i. being of a length in excess of said predetermined distance such that it may rest on, and be supported by, opposing shoulders of adjacent primary support members;

ii. including a vertical web and a transverse flange iii. including means to anchor said hook means when the said first half is brought into web-toweb abutment with the second half and raised and shifted in a first direction parallel to said webs to bring said hook over said anchor means and then lowered, thereby to lock the two halves together in web-to-web abutment with their flanges oppositely directed to constitute and effective T-spline; whereby the ceiling tiles may be demounted by raising said first half by the clip means and shifting it in a second direction opposite the first direction, thereby unlocking said hook from the anchoring means and lowering the first half by pulling downwardly on the clip means, and then enabling the edge of the tile supported by each said first half of the device also to be lowered and removed from the ceiling. 

1. A downward access disengageable T-spline device for use in demountable supporting at least two tiles of a suspended ceiling system on the opposing shoulders of a pair of parallel primary support members spaced from each other by a predetermined distance, said device comprising: A. A first half, said first half i. being of a length not greater than said predetermined distance; ii. having a vertical web and a transverse flange extending laterally from said web; iii. including at least one hook-like element having hook means, said element being partially punched out of said vertical web and bent back upwardly upon the web to extend its hook means above said web with its hook facing downwardly, and iv. clip means attachable to said web and extendable below said transverse flange; and B. a second half, said second half i. being of a length in excess of said predetermined distance such that it may rest on, and be supported by, opposing shoulders of adjacent primary support members; ii. including a vertical web; a first transverse flange extending laterally from the lower edge of latter web in a direction opposite to that of the flange of the first half, whereby the two halves may be brought together and secured by placing their webs in abutment to form a T-member; and a second flange extending from the upper edge of said web of the second half in a direction opposite the direction of the first transverse flange, thereby to constitute a member having a Z-type cross section; and iii. including first slotting in the said second flange to permit said extending hook means to pass upwardly through said second flange, and second slotting to receive said hook means of sAid hook-like element on the first half when the latter is lifted and shifted relative to the second half, thereby to insert said hook means into the said second slotting and to lock the two halves together in web-to-web abutment with their flanges oppositely directed to constitute an effective T-spline, whereby the ceiling tiles may be demounted by pushing said first half upwardly by means of said clip means and shifting said first half relative to the second half to remove the hook means from the second slitting and to enable it to be drawn downwardly through the first slotting, whereupon said first half may be pulled down from its engagement with the second half and the edge of the tile supported by said first half of the device may be lowered and removed from the ceiling.
 1. A downward access disengageable T-spline device for use in demountable supporting at least two tiles of a suspended ceiling system on the opposing shoulders of a pair of parallel primary support members spaced from each other by a predetermined distance, said device comprising: A. A first half, said first half i. being of a length not greater than said predetermined distance; ii. having a vertical web and a transverse flange extending laterally from said web; iii. including at least one hook-like element having hook means, said element being partially punched out of said vertical web and bent back upwardly upon the web to extend its hook means above said web with its hook facing downwardly, and iv. clip means attachable to said web and extendable below said transverse flange; and B. a second half, said second half i. being of a length in excess of said predetermined distance such that it may rest on, and be supported by, opposing shoulders of adjacent primary support members; ii. including a vertical web; a first transverse flange extending laterally from the lower edge of latter web in a direction opposite to that of the flange of the first half, whereby the two halves may be brought together and secured by placing their webs in abutment to form a T-member; and a second flange extending from the upper edge of said web of the second half in a direction opposite the direction of the first transverse flange, thereby to constitute a member having a Ztype cross section; and iii. including first slotting in the said second flange to permit said extending hook means to pass upwardly through said second flange, and second slotting to receive said hook means of sAid hook-like element on the first half when the latter is lifted and shifted relative to the second half, thereby to insert said hook means into the said second slotting and to lock the two halves together in web-to-web abutment with their flanges oppositely directed to constitute an effective Tspline, whereby the ceiling tiles may be demounted by pushing said first half upwardly by means of said clip means and shifting said first half relative to the second half to remove the hook means from the second slitting and to enable it to be drawn downwardly through the first slotting, whereupon said first half may be pulled down from its engagement with the second half and the edge of the tile supported by said first half of the device may be lowered and removed from the ceiling.
 2. A downward access disengageable T-spline device for use in demountably supporting at least two tiles of a suspended ceiling system on the opposing shoulders of a pair of parallel primary support members spaced from each other by a predetermined distance, said device comprising: A. a first half, said first half i. being of a length not greater than said predetermined distance; ii. having a vertical web and a transverse flange extending laterally from the bottom edge of said web to constitute an L-shaped member in cross section, and said web being slit to receive a pair of oppositely extending horizontal pins; and iii. including a pair of hook-like elements each having hook means, said elements being partially punched out of said vertical web and bent back upwardly upon the web to extend their hook means above the web with their hooks facing downwardly; and iv. clip means, said clip means including a pair of horizontally extending pin-like ends insertable in said slits in the web and being disposed to protrude below said transverse flange; and B. a second half, said second half i. being of a length in excess of said predetermined distance such that it may rest on, and be supported by, opposing shoulders of adjacent primary support members; ii. including a vertical web and a transverse flange extending from the bottom edge of the latter web in a direction opposite to that of the flange of the first half, whereby the two halves may be brought together and secured by placing their webs in abutment to form a T-member; and iii. permitting the hook means of said hook-like elements to be disposed above its vertical web when the first half is placed in web-to-web abutment with the second half and including means to anchor said hook means when the said first half is raised and shifted in a first direction parallel to the second half and then lowered into web-to-web abutment with the second half, thereby to lock the two halves together with their flanges oppositely directed to constitute an effective T-spline; whereby the ceiling tiles may be demounted by raising the first half by the clip means and shifting it in a second direction opposite the first direction, thereby unhooking the hooks of the said hook-like elements from the anchoring means in the said second half, and slidably separating the two halves of said device by pulling downwardly on the clip means, thereby enabling the edge of the tile supported by each said first half of the device also to be lowered and removed from the ceiling.
 3. The device as described in claim 2, wherein the means in said second half of said device to anchor the hooks of the hook-like elements of the first half of said device, comprises a further flange extending from the upper edge of the web parallel to, but oppositely from the other flange on said web, and said further flange having first slotting to permit the upper parts of said hook-like elements to be passed therethrough, and second slotting adjacent the first slotting to receive said hooks. 